I would look at the design delta T in the Sizing:Plant object, compare it to the delta T you actually get when running.
The way plant sizing works, it is the fan coil unit’s design size for water flow rate that matters, not the heating load. Then plant uses the delta T in the sizing object to figure out boiler capacity from the sum of all the fan coil flow requests.
From: EnergyPlus_Support@xxxxxxxxxxxxxxx [mailto:EnergyPlus_Support@xxxxxxxxxxxxxxx]
Sent: Monday, April 20, 2015 12:20 AM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Total heating load boiler 60 % higher than total heating load rooms
I've done a designbuilder simulation of an office building with fan coil units heating and cooling every room.
In Designbuilder you quickly get the total system heating load (the sum of all rooms) and the Boiler total capacity for heating.
I work with efficiency 100% for the boiler, so normally the heating load of all the rooms, must be the total capacity for the boiler.
In this model, the boiler needs 60 % more capacity ( at 7 AM on the coldest morning in the year) then the sum of the heating load of all the rooms. Later the day, the two are loads are almost equally, so it's just at startup in the morning.
According to the DB support this could be the difference between the inertia of water (fan coils) and gas (boiler).
I've never had such a difference. Is this normal?
What will I communicate to the client as Heating capacity for the boiler? The sum of all the rooms ? Or the boiler capacity as calculated ? (which is a lot higher than the sum of all the rooms)
Geert
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Posted by: "Brent Griffith" <Brent.Griffith@xxxxxxxxxxxxxxxxxx>
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